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dos33fsprogs/chiptune_player/rasterbars.s
Vince Weaver af0d298dbe chiptune/mode7: update rasterbars code comments
2018-02-27 22:46:19 -05:00

300 lines
6.3 KiB
ArmAsm
Raw Blame History

; Not quite a raster-bar, but why not
; OPTIMIZATION (as originally it was 16,200 instructions, a bit much
; for a max 20,000 cycle interrupt handler)
; -120 : Unroll the zero loop, saved 120 cycles
; -5000 : Inline the vlin_double code
;===========
; CONSTANTS
;===========
ELEMENTS EQU 64
NUM_ROWS EQU 20
;=====================
; Rasterbars
;=====================
;===========================
;===========================
; Main Loop
;===========================
;===========================
draw_rasters:
; clear rows
; ldy #(NUM_ROWS-1) ; 2
lda #0 ; 2
init_rows:
sta row_color+0 ; 4
sta row_color+1
sta row_color+2
sta row_color+3
sta row_color+4
sta row_color+5
sta row_color+6
sta row_color+7
sta row_color+8
sta row_color+9
sta row_color+10
sta row_color+11
sta row_color+12
sta row_color+13
sta row_color+14
sta row_color+15
sta row_color+16
sta row_color+17
sta row_color+18
sta row_color+19
; sta row_color,Y ; 5
; dey ; 2
; bpl init_rows ; 2nt/3
;==============
; Originally 4+20*10 = 204 cyles / 10 bytes
; now 2+4*20 = 82 cycles / 62 bytes
;================
; set colors
ldy SCREEN_Y ; 3
lda #COLOR_BOTH_DARKBLUE ; d. blue ; 2
jsr set_row_color ; 6+136
lda #COLOR_BOTH_MEDIUMBLUE ; m.blue ; 2
jsr set_row_color ; 6+136
lda #COLOR_BOTH_AQUA ; aqua ; 2
jsr set_row_color ; 6+136
lda #COLOR_BOTH_PINK ; pink ; 2
jsr set_row_color ; 6+136
lda #COLOR_BOTH_RED ; red ; 2
jsr set_row_color ; 6+136
;==============
; new = 5 * 142 = 710
; original = 1152
;=================
; draw rows
ldy #(NUM_ROWS-1) ; 2
draw_rows_loop:
lda row_color,Y ; 5
beq draw_rows_skip ; skip if black ; 2nt/3
sta COLOR ; 3
sty TEMPY ; 3
tya ; y*2 ; 2
asl ; 2
tay ; 2
; hlin_setup inlined
lda gr_offsets,Y ; lookup low-res memory address ; 4
sta GBASL ; 3
iny ; 2
lda gr_offsets,Y ; 4
clc ; 2
adc DRAW_PAGE ; add in draw page offset ; 3
sta GBASH ; 3
ldy #39 ; 2
lda COLOR ; 3
double_loop:
sta (GBASL),Y ; 6
dey ; 2
bpl double_loop ; 2nt/3
ldy TEMPY ; 3
draw_rows_skip:
dey ; 2
bpl draw_rows_loop ; 3/2nt
;==============================
; Original: 20 * 741 = 14,820
; new = 2+ 20*(53+11*40)=9862
; (note, worst case)
;==================
; update y pointer
;==================
ldy SCREEN_Y ; 3
iny ; 2
cpy #ELEMENTS ; 2
bne not_there ; 3/2nt
ldy #0 ; 2
not_there:
sty SCREEN_Y ; 3
rts ; 6
;===========
; 24
;=====================================
; original total= 16,200
; new total (worst case)= 10,678
; (realistic) = 5,748
;===================
;===================
; set_row_color
;===================
;===================
; color in A
; Y=offset
; Y incremented
; A, X trashed
set_row_color:
sta COLOR ; 3
tya ; wrap y offset ; 2
and #(ELEMENTS-1) ; 2
tax ; 2
lda fine_sine,X ; lookup sine value ; 4
; pre-shifted right by 4, sign-extended
; 18 added to center
sin_no_more:
pha ; save row value ; 3
jsr put_color ; put color at row ; 6+44
pla ; restore row value ; 4
clc ; increment row value ; 2
adc #1 ; 2
jsr put_color ; put color at row ; 6+44
iny ; increment for next time ; 2
rts ; 6
;=============
; 132
;==================
; put_color
;==================
; A = row to set color of
; A trashed
put_color:
clc ; 2
ror ; row/2, with even/odd in carry ; 2
tax ; put row/2 in X ; 2
bcc even_line ; if even, skip to even ; 2nt/3
odd_line:
lda #$f0 ; load mask for odd ; 2
bcs finish_line ; 2nt/3
even_line:
lda #$0f ; load mask for even ; 2
finish_line:
sta MASK ; 3
and COLOR ; mask off color ; 3
sta COLOR2 ; store for later ; 3
lda MASK ; 3
eor #$ff ; invert mask ; 2
and row_color,X ; load existing color ; 4
ora COLOR2 ; combine ; 3
sta row_color,X ; store back ; 5
rts ; 6
;===========
; 44
;======================
; some arrays
;======================
row_color:
.byte $00,$00,$00,$00,$00, $00,$00,$00,$00,$00
.byte $00,$00,$00,$00,$00, $00,$00,$00,$00,$00
; arithmatically shifted right by 4, sign extended, added 18 to center
; FIXME: exploit symmetry and get rid of 3/4 of this table
; possibly not worth the extra code
fine_sine:
.byte $00+18 ; 0.000000
.byte $01+18 ; 0.098017
.byte $03+18 ; 0.195090
.byte $04+18 ; 0.290285
.byte $06+18 ; 0.382683
.byte $07+18 ; 0.471397
.byte $08+18 ; 0.555570
.byte $0A+18 ; 0.634393
.byte $0B+18 ; 0.707107
.byte $0C+18 ; 0.773010
.byte $0D+18 ; 0.831470
.byte $0E+18 ; 0.881921
.byte $0E+18 ; 0.923880
.byte $0F+18 ; 0.956940
.byte $0F+18 ; 0.980785
.byte $0F+18 ; 0.995185
.byte $0F+18 ; 1.000000
.byte $0F+18 ; 0.995185
.byte $0F+18 ; 0.980785
.byte $0F+18 ; 0.956940
.byte $0E+18 ; 0.923880
.byte $0E+18 ; 0.881921
.byte $0D+18 ; 0.831470
.byte $0C+18 ; 0.773010
.byte $0B+18 ; 0.707107
.byte $0A+18 ; 0.634393
.byte $08+18 ; 0.555570
.byte $07+18 ; 0.471397
.byte $06+18 ; 0.382683
.byte $04+18 ; 0.290285
.byte $03+18 ; 0.195090
.byte $01+18 ; 0.098017
.byte $00+18 ; 0.000000
.byte ($FE+18)&$ff ; -0.098017
.byte ($FC+18)&$ff ; -0.195090
.byte ($FB+18)&$ff ; -0.290285
.byte ($F9+18)&$ff ; -0.382683
.byte ($F8+18)&$ff ; -0.471397
.byte ($F7+18)&$ff ; -0.555570
.byte ($F5+18)&$ff ; -0.634393
.byte ($F4+18)&$ff ; -0.707107
.byte ($F3+18)&$ff ; -0.773010
.byte ($F2+18)&$ff ; -0.831470
.byte ($F1+18)&$ff ; -0.881921
.byte ($F1+18)&$ff ; -0.923880
.byte ($F0+18)&$ff ; -0.956940
.byte ($F0+18)&$ff ; -0.980785
.byte ($F0+18)&$ff ; -0.995185
.byte ($F0+18)&$ff ; -1.000000
.byte ($F0+18)&$ff ; -0.995185
.byte ($F0+18)&$ff ; -0.980785
.byte ($F0+18)&$ff ; -0.956940
.byte ($F1+18)&$ff ; -0.923880
.byte ($F1+18)&$ff ; -0.881921
.byte ($F2+18)&$ff ; -0.831470
.byte ($F3+18)&$ff ; -0.773010
.byte ($F4+18)&$ff ; -0.707107
.byte ($F5+18)&$ff ; -0.634393
.byte ($F7+18)&$ff ; -0.555570
.byte ($F8+18)&$ff ; -0.471397
.byte ($F9+18)&$ff ; -0.382683
.byte ($FB+18)&$ff ; -0.290285
.byte ($FC+18)&$ff ; -0.195090
.byte ($FE+18)&$ff ; -0.098017
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